The present invention relates to, in general, the gas counting method and, in particular, to a compensation for variations in counting efficiency due to the quenching effect provided by substances included in a sample gas, the radioactivity of which is to be measured.
In case where a radioactivity of a gaseous sample containing substance or substances providing quenching effect is to be measured, it is known that the counting efficiency is lowered by the quenching effect, resulting in that a precise measurement of the radioactivity of the sample becomes impossible. It has been known that the gas counting method can be classified generally to the batch system and the flow system. In the batch system, the correction for the quenching effect is usually performed by sufficiently refining the sample gas, measuring the radioactivity thereof, preparing the same amount of a standard gas having the same chemical structure as those of the sample gas, measuring the radioactivity thereof and comparing the measured results. On the other hand, in the conventional flow system, the problem due to the quenching effect is resolved by selecting chemical structure of the sample as compound or compounds providing no quenching effect so that any component which would otherwise provide the variation of counting efficiency could be removed as complete as possible.
In any case, the conventional system employs as the main part thereof a pretreatment of the sample gas to avoid the quenching effect which is absolutely necessary to be removed. However, as well known, the pretreatment of the sample gas is not only relatively difficult but also requires a time consuming works and corresponding expenses. In addition to these disadvantages, there is a possibility of mixing in of an uncertainty, making the pretreatment undesirable.